Terminal Sliding Mode Control of UPS Inverters

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Some calamities, such as earthquake and typhoon would cause failure of the power system. In order to ensure that the computer and communication systems operate normally and con-tinuously, we must have a highly reliable power system in now-adays. For the demand of high quality power system, an interruptible power supply (UPS) is generally used for supplying critical loads. However, some of loads of an uninter-ruptible power supply may be nonlinear and will draw current from the inverters with severe distortion. For this reason, the control design of uninterruptible power supply inverters with terminal sliding mode is proposed in this thesis. Using the terminal sliding mode controller, we can not only drive the system state variables to reach and retain in the sliding mode, but the system state variables also reach the system equilibrium point in finite time. Owing to the robust-ness of sliding mode control, the output voltage of inverters has the features of low distortion, and insensitivity to load and input voltage variations. According to terminal sliding mode control law, we can obtain modulated inverters through pulse-width-modulation (PWM). System simulation results are presented to confirm that the proposed sliding mode controller can achieve satisfactory response under different kinds of loads.